The 3D-NTT instument

Michel MARCELIN (LAM)

The 3D-NTT is a visible integral field spectro-imager offering two modes. A low resolution mode (R ~ 300 to 6 000) with a large field of view Tunable Filter (17'x17') and a high resolution mode (R ~ 10 000 to 40 000) with a scanning Fabry-Perot (8.5'x8.5'). It will be operated as a visitor instrument on the NTT from 2010. A lot of programs will be led with this instrument, most of them dealing with the evolution of galaxies. The low resolution mode will provide monochromatic images of the targets in the light of selected lines (then enabling to produce line ratios maps) while the high resolution mode will provide velocity fields.

Two large programmes, to be led with the 3D-NTT, have been approved by ESO's OPC : "Characterizing the interstellar medium of nearby galaxies with 2D maps of extinction and abundances" (PI M. Marcelin) and "Gas accretion and radiative feedback in the early universe" (PI J. Bland Hawthorn). Both are mainly based on the Tunable Filter mode.

The 3D-NTT is being built as a collaborative effort between LAM (Marseille), GEPI (Paris) and LAE (Montréal).

The other Tunable Filters operating by now on telescopes are MMTF on Magellan and OSIRIS on Grantecan. There is also a project, named BTFI, on SOAR. Compared with these instruments, the main advantages of the 3D-NTT are:

     - Large Field of View 17’x17’ (much better than BTFI, 3’ and OSIRIS 6.7’ but smaller than MMTF 27’) and a FOV 10’ Ø without "phase-shift" effect.

    - Blue sensitivity (MMTF only operates above 500nm).

    - Possibility of high resolution mode (also possible on BTFI but not possible on MMTF nor OSIRIS).

The main disadvantages of the 3D-NTT are :

- No Adaptive Optics (note however that seeing at NTT is often around 0.5 arcsec).

- It is a visitor instrument (hence not maitained by local staff).

The website adress of the instrument is : http://www.astro.umontreal.ca/3DNTT.